Kip Warner wrote:
> Thanks Bob. Makes perfect sense. Are the child directories in /usr
> precede /usr/local in the order in which they appear in the path
> environment variable?
I did not quite follow the question but will try to answer it anyway.
Usually a user's environment will include their personal directories,
the system local directories, and official system directories.
Basically these in pretty much this order:
PATH=$HOME/bin:/usr/local/bin:/usr/bin:/bin
This allows a priority of program selection with the version preferred
by the user first, the local admin second and the system third. That
is not an exclusive list. Both FHS and non-FHS systems have other
directories too (e.g. /opt/bin, /usr/ccs/bin, /usr/xpg4/bin, etc.) but
for the sake of this discussion the above is a good place to start.
The above works as a good default.
Most system processes will be just like the above but without any
user's home and with the system binary directory. (Used to be
statically linked system directory, but that is another story.)
PATH=/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
But some system processes will want to avoid commands other than
exactly the ones they are designed to work with and tested. There may
be security implications in some cases. Those commands will eschew
non-system directories and stick to just the system installed
commands.
PATH=/usr/bin:/bin:/usr/sbin:/sbin
It is a judgement call as to which PATH any particular process uses.
And different systems lean toward slightly different operating and
security models than others and so there are variations. Some use
'staff' sgid directories, 'wheel' groups, etc. All generalities are
false, including this one.
Bob
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Received on Sun Aug 20 23:51:44 2006